Evening star. [volume] (Washington, D.C.) 1854-1972, 1887-06-25
THE WEB WORMS AGAIN.
FfOfs Riley Writes n Letter TOuchtn0
Many Points of Interest.


THE WORMS THAT DO THE DAMAeE-sTArrsTIcs Az
70 THEM RATE OF INcKEAsE-A PLEA IN FAVOR
OF ARsENIcAL sPRAY-MIsTAKEs MADE IN THE
IDENTITY OF WORMS.
Prof. C. v. Riley, the entomoogist Of the Agrf-
cultural Department, has occasion at this season
TO answer all sorts OF inquiries about injurious in
secta The following reply OF the 18th inst. to
sundry inquiries from one OF our citizens touches
several matters OF interest to Washingtonians.
Prot Riley wrote: "Your letter Of yesterday has
come to hand. You are evidently laboring under
Misrepresentation IS to the habits Of the insect
which was so abundant upon our shade trees last
season. and which Just now Is renewing its injury.
The insect, which was so numerous as to dwarf
all others. was the fall web worm hyphants1o
cuneu). and the eggs OF this insect are not con-
tanned in the winter cocoOns. These cocoons con-
tain the insect in the quiescent or pupa state. II
these cocoons were the ones DESTROYED by you the
amount OF good accomplished may be estimated
BY dividing the number destroyed by and then
multiply by 500, as probably half OF them only
were females, and as each female lays in the
netghborhood OF 500 eggs This estimate, how
half on account OF the great number OF pupR
which were infested by parasites and by fungus
disease e The Socoons collected last winter from
the branches or the trees were not those OF this
species, but the pendant bags Of
THE BAG-woRM,
another insect which Is doing considerable DAM
age, although not so much as the web-worm. The
bag passes the winter In the egg state in
the bag and each sound female bag contains 900
or 200 eggs, but hardly one in dozen or the bags
picked from the trees at that season OF the year
contains eggs Many Of them are empty old bags;
Or last years bags contain the empty shell OF the
male pupa from which the moths issued the pre-
do not know whether you have seen my recent
bulletin on Our Shade Trees and their Insect Defo
nators" bulletin No. 10 OF this diviSion). take
pleasure Ih sending you copy and can spare you
VIII md very fun consideration of all the mere
Important facts known OF the four chief defolta-
and also recommendations for their control feel
quite sure that you will appreciate what have
SAID the more you become familiar with these in
inendattons made are not the blind and narrow
deductions OF inexperience, but are based upon
while I lived in the West, as well as during the
time have resided in Washington. They are also
based on actual experience and experiment which
have proved satisfactory. ! would not In any way
weaken the coinmendable efforts to destroy the
web-wOrm by pruning, and you viii md that in
the bulletin lay stress the Importance Of this
during the winter months against the bag-worm,
and during the last Of May and first OF June
against the web-worm. The value OF co-opera-
OF obligatory laws IS not so clear for reasons that
would too greatly lehgthen this letter to discuss.
ARsENTCAL SPRAYS.
"Your prejudice against the arsenical sprays Is
unfounded, as they are the only wholesale means
at our command with which to protect the trees
when the pest has become widespread, whether in
the first or second generations They are, In fact,
the most rapid and simplest even against the 1rSI
o10 You have been BY
again the present year In our local journals, par
ticularly by one Individual Who'll fond OF address
Ing the pubic, and who, by the verdict OF those
VINO have been most Intimately associated with
him, Is about As "unpract1car Ia this field as
IT Is possible TO be. You Will ind that against
rr0 n r har-0 ryrnp nf
destroying the cocoons with their chrysaltdes and
the early summer work u pruning and burning
the young colonies as soon as by their webs they
become visible. i have urged this particularly
upon such streets as have the Negundo ocer0ides,
or the box elder, because or the preference OF the
species for this tree have also pointed out how
the worms may De burned in various ways upon
the tree and discussed other matters bearing upon
the general treatment OF the trees SO far as this
insect Is concerned. The arsenicA washes when
used as recommended by me, have, however, the
great advantage over all other means that they
not only Kill the worms which have already
Matched but have more or less prolonged pro-
tective effect and leave the trees unmut1lated.
Take, as an illustration, street northwest. Not
withstandlng The pruning that has been done In
the city this season the most OF the box elders
along that street al tine present time are almost
entirely skeleton1zed, E.. the great mass of the
are enectually webbed, so that neither pruning
nor burning can very wen be reSorted to without
very materially cutting back and d1srguring the
trees. These trees, as suggested in my bulletin,
could have been sprayed toward the end or May,
before any OF the worms ha0 Matched from their
numerous egg masses, which past experience 1ndi-
Gated would be found upon them The young
WORMS upon Matching would at once have per-
ished without disngultng the trees, and this over
period OF two Or three weeks.
THE BOZ HLDERs.
"Some surprise has been expressed that the
worms should be SO numerous on these trees after
so much care was had last winter to destroy the
eocoons on their boxes A great many such
cocoOns escaped vigilance under the caves and
lxflfy nf httflf
the whole nelgnburnood OF Sucn box elders are
instinct1vely attracted TO them Tor PURPOSES OF
opposition, as have shown in the aforesaid bull
etln. These trees Unless sprayed (and tnere Is NO
,Iuie 10 lose now) Will 1urI more moths for
breeding the second generation OF worms tnan,
perhaps, all the rest OF the trees in District
and 10 allow them to render thousand-rold more
difficult the task OF battling with the second gen.
eralion ON foolish, sentimental grounds, Is viz.
and most unwise.
You may not know 1t, but proper spraying of
the arsenical washes is not mere suggestion.
Their Use naS long since become general For
about dozen years now they nave been exten-
sivey resOrted TO- not only TO protect shade trees
out 10 protect our orchards. Properly sprayed
should never DC coliOus enough to produce that
result. In TACT II dries within few minutes after
Application, ieavlng but an lmpalp dDie powder,
cnlrny on the under surface or the leaves.
IL does not necessarily cause the leaves TO drop
when properly applied, and am not aware that
leaves 10 the ndoil Of dropping extensively at
this season OF tne Year. Wn1ie approaching your
fear IN reference TO children l feel neyertnee 8
that IL Is unIouaded, Ior even II They were IN the
habit OF eating leaves, Which Is certainly con-
lrary 10 my experience, they would have TO eat
an enormous quantity from poisoned tree 10 be
In any Way lnJuTiUusly affected ny the poison.
LITTLE DANGER TO CHILDREN.
ga few definite ngures will, perhaps better than
anything else, show the baselessneSs OF this fear
OF injury to children. One pound OF London pur-
pie 70 100 gallons OF water Is very good propor.
ZION, ami Abundi ntly effective when properly
sprayed. medium-siZed shade tree may Ue
el1eetuaIly sprayed with gallon OF TIL, mixture
| OF Arsenic. Hence, there would be upon such q
tree after one application 1900 OF pound, or
about 23 grains OF arsenic. i leave you TO esri.
mate the number or leaves upon one or our
ordinary shaue trees-pr0oably from 10000 10
70,OUoNand the consequent lnnDlteaimal Quantity
Oh the poison upon ieAf. In pUInJ on fact how.
ever, but limited portion or each tree O.. q
the weo-worn after II has once made its appear.
ance, except upon such trees as the box elder.
where IL may be expected TO reach over the
greater portion OF the trees. Again. the best tune
| Tor spraying Is on cloudy days or early In the
morning before the dew has evaporated and
| children are not generally about At that time,
This spraying In ordinary seasons may he unnec-
essary except on the box elders. / would always
spray them thoroughly the last week OF May aud
| the other trees only partially except In excep-
uonal years IKE 1856.
You will ind the trees In my grounds at the
northwest corner OF 18th and streets UNAFFECTED
by any OF these worms and that the elmS remaiD
badly rldaled by the elm-leaf beetle. The reasOI
| Is that nave sprayed my trees with London pur
| pie, and may say that my four children rur
around In the yard whenever IL Is pleasant enough